An image processing apparatus is known which comprises an image forming section for forming an image on a sheet and an image erasing section for erasing the image by heating the sheet. A plurality of cassettes is used in the image processing apparatus, including: a cassette in which a used sheet is accommodated, a cassette in which a sheet subjected to an erasing processing is accommodated and a cassette in which a new sheet is accommodated.
To conform to the sizes of a variety of sheets, each cassette is equipped with a mechanism by means of which the size of the sheet capable of being accommodated in the cassette can be manually changed. Further, in order to match the size of accommodated sheet with a cassette for accommodating a sheet prior to the erasing processing and a cassette for accommodating a sheet subjected to the erasing processing, a user manually adjusts to make the size of each cassette match with the size of the sheet.
However, if the user changes the size of the sheet accommodated in one of cassettes and then carries out a processing without changing the size of the sheet accommodated in other one of cassettes, then there is a case in which the non-matching of the accommodated sheets in size leads to a jam or the damage of a sheet.